金属Sc对Ti-6Al-4V合金组织演变与性能的影响

Influence of Sc on microstructure evolution and property of Ti-6Al-4V alloy

采用真空电弧熔炼技术制备了含Sc(质量分数)为0,0.1%,0.3%,0.5%的4种Ti6Al4V合金,并利用X射线衍射技术、光学金相显微镜和SHIMADZUHMV硬度计对铸态合金的相组成、等温退火后进行淬火的合金的显微组织和显微硬度进行研究。研究结果表明在合金的铸态组织中存在大量的类魏氏组织,添加金属Sc减小了魏氏组织的含量与尺寸;经过等温退火及淬火处理后,在合金组织中存在细针状的马氏体组织和少量的类魏氏体组织,同时,随着退火温度的降低,组织中针状马氏体尺寸减小,金属Sc对合金组织起明显的细化作用;在铸态合金中存在的相为Ti3Al,添加金属Sc使αTi在低角度的衍射峰强度变弱,在高角度的衍射峰强度变强;添加金属Sc导致Ti6Al4V合金片层组织的显微硬度大幅度提高,当Sc含量在0.1%～0.3%时,其显微硬度最适宜;退火态合金的显微硬度比铸态合金的显微硬度提高了很多;金属Sc对αTi的固溶强化效果最明显。

Four kinds of Ti-6Al-4V alloys containing Sc content of 0, 0.1%, 0.3%, 0.5% were prepared by vacuum arc remelting technique respectively. By using X-ray diffraction technique and optical microscopy (OM) and SHIMADZU HMV microhardness tester, the phase of as-cast alloys, microstructure and microhardness were analyzed respectively. The results show that the microstructure of as-cast alloys exhibits the feature of Widmanst tten structure, the size and content are decreased by the addition of metal Sc; the needle-like martensitic structure and traces of Widmanst tten structure appear in the microstructure of alloy under the isothermal annealing and quenching treatment, and with the decrease of annealing temperature the grain size of needle-like martensite decreases; Sc refines the microstructure of alloy significantly. The main phase in the alloy is Ti3Al. Due to the addition of Sc, the diffraction peaks of α-Ti in lower angle regions become weaker, while the peaks in higher angle regions become stronger; the addition of Sc improves the microhardness of lamellar microstructure remarkably. The highest microhardness is obtained with a content of scandium 0.1%-0.3%. The microhardness of as-annealed alloy is higher than that of as-cast alloys. The solid solution strengthening effect of Sc on α-Ti is very evident.